Resist composition and method for producing resist pattern

ABSTRACT

A resist composition contains (A) a resin having a structural unit represented by the formula (I), (B) an acid generator and (D) a compound represented by the formula (II), 
     
       
         
         
             
             
         
       
     
     wherein R 1 , ring X 1 , R 3 , R 4 , m, and n are defined in the specification.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Application No. 2011-39448 filed on Feb. 25, 2011. The entire disclosures of Japanese Application No. 2011-39448 is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resist composition and a method for producing resist pattern.

2. Background Information

A resist composition which includes a resin polymerized from 2-ethyl-2-adamantyl methacrylate, 3-hydroxy-1-adamanthyl methacrylate and α-methacryloyloxy-γ-butyrolactone; an acid generator containing triphenyl sulfonium-1-((3-hydroxy adamantyl)methoxycarbonyl) difluoromethane sulfonate; a quencher containing 2,6-diisopropyl aniline; and a solvent is described in Patent document, JP2006-257078A.

However, focus margin evaluation and pattern line edge roughness of the resist pattern manufactured with the conventional resist composition may be not always satisfied with.

SUMMARY OF THE INVENTION

The present invention provides following inventions of <1> to <6>.

<1> A resist composition contains

(A) a resin having a structural unit represented by the formula (I),

(B) an acid generator and

(D) a compound represented by the formula (II).

wherein R¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms;

ring X¹ represents a C₂ to C₃₆ heterocyclic group, one or more hydrogen atoms contained in the heterocyclic group may be replaced by a halogen atom, a hydroxy group, a C₁ to C₂₄ hydrocarbon, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group;

wherein R³ and R⁴ in each occurrence independently represent a C₁ to C₁₂ hydrocarbon group, a C₁ to C₆ alkoxyl group, a C₂ to C₇ acyl group, a C₂ to C₇ acyloxy group, a C₂ to C₇ alkoxycarbonyl group, a nitro group or a halogen atom;

m and n independently represent an integer of 0 to 4.

<2> The resist composition according to <1>, wherein the structural unit represented by the formula (I) is a structural unit represented by the formula (IA);

wherein R²³ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms;

R²⁴ and R²⁵ in each occurrence independently represent a hydrogen atom or a C₁ to C₂₄ hydrocarbon group, and R²⁶ to R²⁹ independently represent a hydrogen atom or a C₁ to C₂₄ hydrocarbon group, or at least two of R²⁴ to R²⁹ may be bonded together to form a C₃ to C₃₀ ring, one or more hydrogen atoms contained in the hydrocarbon group or the ring may be replaced by a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group, and one or more —CH₂— contained in the hydrocarbon group or the ring may be replaced by —CO— or —O—;

n′ represents an integer of 0 to 3.

<3> The resist composition according to <1> or <2>, wherein the structural unit represented by the formula (I) is a structural unit represented by the formula (IB);

wherein R³⁹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms;

R⁴⁰, R⁴¹, R⁴⁷ and R⁴⁸ in each occurrence independently represent a hydrogen atom or a C₁ to C₂₄ hydrocarbon group, and R⁴² to R⁴⁶ and R⁴⁹ independently represent a hydrogen atom, or a C₁ to C₁₂ hydrocarbon group, or at least two of R⁴⁰ to R⁴⁹ may be bonded together to form a C₃ to C₂₄ ring, one or more hydrogen atoms contained in the hydrocarbon group or the ring may be replaced by a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group, and one or more —CH₂— contained in the hydrocarbon group or the ring may be replaced by —CO— or —O—;

n4 and n5 independently represent an integer of 0 to 3.

<4> The resist composition according to any one of <1> to <3>, wherein the structural unit represented by the formula (I) is a structural unit represented by the formula (ID);

wherein R³¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms;

R³² in each occurrence represents a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group;

n9 represents an integer of 0 to 8.

<5> The resist composition according to any one of <1> to <4>, which further comprises a solvent.

<6> A method for producing resist pattern comprises steps of;

(1) applying the resist composition according to any one of <1> to <5> onto a substrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

According to the resist composition of the present invention, it is possible to achieve satisfactory wide focus margin (DOF) and excellent pattern line edge roughness in the obtained resist pattern.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

“(Meth)acrylic monomer” means at least one monomer having a structure of “CH₂═CH—CO—” or “CH₂═C(CH₃)—CO—”, as well as “(meth)acrylate” and “(meth)acrylic acid” mean “at least one acrylate or methacrylate” and “at least one acrylic acid or methacrylic acid,” respectively.

<Resist Composition>

The resist composition of the present invention contains;

(A) a resin having a structural unit represented by the formula (I) described above (hereinafter may be referred to as “resin (A)”),

(B) an acid generator (hereinafter may be referred to as “acid generator (B)”) and

(D) a compound represented by the formula (II) described above. (hereinafter may be referred to as “compound (II)” or “compound (D)”).

Further, the present resist composition preferably contains a solvent (hereinafter may be referred to as “solvent (E)”) as needed.

<Resin (A)>

The resin (A) has a structural unit represented by the formula (I) (hereinafter may be referred to as “structural unit (I)”).

The resin (A) is preferably a resin having properties which is insoluble or poorly soluble in alkali aqueous solution, but becomes soluble in an alkali aqueous solution by the action of an acid. Here “a resin having properties which is insoluble or poorly soluble in alkali aqueous solution, but becomes soluble in an alkali aqueous solution by the action of an acid” means a resin that is insoluble or poorly soluble in aqueous alkali solution before contact with the acid, and becomes soluble in aqueous alkali solution after contact with an acid. Therefore, the resin (A) is preferably a resin having at least one structural unit (I) and a structural unit derived from a monomer having an acid labile group described below (hereinafter may be referred to as “acid labile monomer (a1)”).

The resin (A) may contain a structural unit other than the structural unit (I) and a structural unit derived from the acid labile monomer (a1). Such structural unit may be structural units derived from a monomer which does not have the acid labile group (hereinafter may be referred to as “acid stable monomer”), or a monomer which is known in this field.

<Structural Unit (I)>

The structural unit (I) is presented by the formula (I) described below,

wherein R¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms;

ring X¹ represents a C₂ to C₃₆ heterocyclic group, one or more hydrogen atoms contained in the heterocyclic group may be replaced by a halogen atom, a hydroxy group, a C₁ to C₂₄ hydrocarbon, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group.

In the formula (I), examples of the halogen atom include fluorine, chlorine, bromine and iodine atom.

Examples of the alkyl group include methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, tert-butyl, iso-butyl, n-pentyl, iso-pentyl, tert-pentyl, neo-pentyl, 1-methylbutyl, 2-methylbutyl, n-hexyl, 1-methylpentyl, 1,2-dimethylpropyl, and 1-ethylpropyl groups.

Examples of the alkyl group which may have a halogen atom include trifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl, perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl, perfluoropentyl and perfluorohexyl groups.

The heterocyclic group may be a group containing —CO— and a nitrogen atom as ring constituting atoms, it may be any of an aromatic heterocyclic or a non-aromatic heterocyclic group, and any of a monocyclic or a polycyclic group.

Specific examples of the group below include as follows.

The hydrocarbon group may be any of an alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group and a combination of two or more such groups.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic hydrocarbon group. Examples of the monocyclic hydrocarbon group include a cycloalkyl group such as cyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, cycloheptyl and cyclooctyl, groups. Examples of the polycyclic hydrocarbon group include decahydronaphtyl, adamantyl, norbornyl, methylnorbornyl groups and a group as follows.

Examples of the aromatic hydrocarbon group include an aryl group such as phenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl, p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl, phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the alkoxyl group include methoxy, ethoxy, propoxy, propoxy, butoxy, pentyloxy, n-hexyloxy, heptyloxy, octyloxy, decyloxy and dodecyloxy groups.

Examples of the acyl group include acetyl, propionyl and butyryl groups.

Examples of the acyloxy group include acethyloxy, propyonyloxy, butyryloxy and iso-butyryloxy groups.

In the formula (I), R¹ is preferably a hydrogen atom or methyl group.

Ring X¹ is preferably a 4 to 7-membered heterocyclic group containing a nitrogen atom or a heterocyclic group containing the 4 to 7-membered heterocyclic group, and more preferably a 4 to 6-membered heterocyclic group containing a nitrogen atom or a heterocyclic group containing the 4 to 6-membered heterocyclic group. The —CO— is preferably positioned so as to bond to the nitrogen atom, that is, ring X¹ is preferably a lactam ring.

As the structural unit (I), either a structural unit represented by the formula (IA), a structural unit represented by the formula (IB), a compound represented by the formula (ID), a structural unit represented by the formula (IC) or a structural unit represented by the formula (IE) is preferable.

wherein R²³ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms;

R²⁴ and R²⁵ in each occurrence independently represent a hydrogen atom or a C₁ to C₂₄ hydrocarbon group, and R²⁶ to R²⁹ independently represent a hydrogen atom or a C₁ to C₂₄ hydrocarbon group, or at least two of R²⁴ to R²⁹ may be bonded together to form a C₃ to C₃₀ ring, one or more hydrogen atoms contained in the hydrocarbon group or the ring may be replaced by a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group, and one or more —CH₂— contained in the hydrocarbon group or the ring may be replaced by —CO— or —O—;

n′ represents an integer of 0 to 3.

wherein R³⁹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms;

R⁴⁰, R⁴¹, R⁴⁷ and R⁴⁸ in each occurrence independently represent a hydrogen atom or a C₁ to C₂₄ hydrocarbon group, and R⁴² to R⁴⁶ and R⁴⁹ independently represent a hydrogen atom or a C₁ to C₁₂ hydrocarbon group, or at least two of R⁴⁰ to R⁴⁹ may be bonded together to form a C₃ to C₂₄ ring, one or more hydrogen atoms contained in the hydrocarbon group or the ring may be replaced by a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group, and one or more —CH₂— contained in the hydrocarbon group or the ring may be replaced by —CO— or —O—;

n4 and n5 independently represent an integer of 0 to 3.

wherein R⁵² represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms;

-   -   R⁵³, R⁵⁴, R⁶³, R⁶⁴, R⁶⁶ and R⁶⁷ in each occurrence independently         and R⁵⁵ to R⁶², R⁶⁵ and R⁶⁸ independently represent a hydrogen         atom or a C₁ to C₁₂ hydrocarbon group, or at least two of R⁵³ to         R⁶⁸ may be bonded together to form a C₃ to C₁₈ ring, one or more         hydrogen atoms contained in the hydrocarbon group or the ring         may be replaced by a halogen atom, a hydroxy group, a C₁ to C₁₂         alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or         a C₂ to C₄ acyloxy group, and one or more —CH₂— contained in the         hydrocarbon group or the ring may be replaced by —CO— or —O—;

n6, n7 and n8 independently represent an integer of 0 to 3.

wherein R³¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms;

R³² in each occurrence independently represents a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group;

n9 represents an integer of 0 to 8.

wherein R³³ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms;

R³⁴ in each occurrence independently represents a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group;

n10 represents an integer of 0 to 14.

Examples of the ring formed by bonding at least two of R²⁴ to R²⁹, R⁴⁰ to R⁴⁹, or R⁵³ to R⁶⁸ include the same heterocyclic groups as described above.

n′ is preferably 0 or 1, and more preferably 0.

n4 is preferably 0 or 1, and more preferably 0.

n5 is preferably 1 or 2, and more preferably 1.

n6 is preferably 0 or 1, and more preferably 0.

n7 is preferably 0 or 1, and more preferably 0.

n8 is preferably 0 or 1, and more preferably 1.

n9 is preferably 0 or 1, and more preferably 0.

n10 is preferably 0 or 1, and more preferably 0.

Example of the structural unit (I) include structural units below.

Also, examples of the structural units (I) include structural units in which a methyl group corresponding to R³ in the structural units represented by the above is replaced by a hydrogen atom.

Among these, the structural unit represented by the formula (IA), the structural unit represented by the formula (IB) and the structural unit represented by the formula (ID) are preferable, and the structural unit represented by the formula (ID) is more preferable.

The structural unit (I) is derived from a compound represented by the formula (I′) (hereinafter may be referred to as “compound (I′)”).

wherein ring X¹ and R¹ represent the same meaning as described above.

The compound represented by the formula (I′) can be produced according to the method below.

The compound represented by the formula (I′) can be obtained by reacting a compound represented by the formula (I-a) with a compound represented by the formula (I-b) in presence of a catalyst in a solvent. Preferred examples of the catalyst include N-methylpyrrolidine. Preferred examples of the solvent include N,N-dimethylformamide.

wherein ring X¹ and R¹ represent the same meaning as described above;

X represents a halogen atom or (meth)acryloyloxy group.

Examples of the halogen atom include fluorine, chlorine, bromine or iodine atom. The chlorine atom is preferable.

Example of the compound represented by the formula (I-a) include, for example, compounds below. Commercially available compounds are used as these.

The compound represented by the formula (I-a-1) can be obtained by reacting cyclophentene with chlorosulfonyl isocyanate (see, JP2007-514775A).

Examples of the compound represented by the formula (I-b) include methacrylic chloride and methacrylic anhydride.

The resin (A) may be contain a structural unit other than the structural unit (I) as described above, the proportion of the structural unit (I) in the resin (A) is generally 1 to 100 mol %, preferably 5 to 95 mol %, more preferably 5 to 50 mol %, and still more preferably 5 to 30 mol %, with respect to the total structural units (100 mol %) constituting the resin (A).

For achieving the proportion of the structural unit (I) in the resin (A) within the above range, the amount of the compound (I′) to be used can be adjusted with respect to the total amount of the monomer to be used when the resin (A) is produced (the same shall apply hereinafter for corresponding adjustment of the proportion).

The resin (A) is preferably a resin polymerized from at least one compound (I′) and an acid labile monomer (a1), and more preferably a resin polymerized from at least one compound (I′), the acid labile monomer (a1), and the acid stable monomer.

<Acid Labile Monomer (a1)>

The “acid labile group” means a group which has an elimination group and in which the elimination group is detached by contacting with an acid resulting in forming a hydrophilic group such as a hydroxy or carboxy group. Examples of the acid labile group include a group represented by the formula (1) and a group represented by the formula (2). Hereinafter a group represented by the formula (1) may refer to as an “acid labile group (1)”, and a group represented by the formula (2) may refer to as an “acid labile group (2)”.

wherein R^(a1) to R^(a3) independently represent a C₁ to C₈ alkyl group or a C₃ to C₂₀ alicyclic hydrocarbon group, or R^(a1) and R^(a2) may be bonded together to form a C₂ to C₂₀ divalent hydrocarbon group, * represents a bond. In particular, the bond here represents a bonding site (the similar shall apply hereinafter for “bond”).

wherein R^(a1′) and R^(a2′) independently represent a hydrogen atom or a C₁ to C₁₂ hydrocarbon group, R^(a3′) represents a C₁ to C₂₀ hydrocarbon group, or R^(a2′) and R^(a3′) may be bonded together to form a C₂ to C₂₀ divalent hydrocarbon group, and one or more —CH₂— contained in the hydrocarbon group or the ring may be replaced by —O— or —S—, * represents a bond.

Examples of the alkyl group of R^(a1) to R^(a3) include methyl, ethyl, propyl, butyl, pentyl and hexyl groups.

Examples of the alicyclic hydrocarbon group of R^(a1) to R^(a3) include a monocyclic or polycyclic hydrocarbon groups such as cyclopentyl, cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, cycloheptyl, cyclooctyl groups; and polycyclic hydrocarbon groups such as decahydronaphtyl, adamantyl, norbornyl (i.e., bicyclo[2.2.1]hexyl), and methyl norbornyl groups as well as groups as below.

The alicyclic hydrocarbon group of R^(a1) and R^(a2) preferably has 3 to 16 carbon atoms.

When R^(a1) and R^(a2) is bonded together to form a C₂ to C₂₀ hydrocarbon group, examples of the group-C(R^(a1))(R^(a2))(R^(a3)) include groups below. The divalent hydrocarbon group of R^(a1) and R^(a2) preferably has 3 to 12 carbon atoms.

Specific examples of the acid labile group (1) include, for example,

1,1-dialkylalkoxycarbonyl group (a group in which R^(a1) to R^(a3) are alkyl groups, preferably tert-butoxycarbonyl group, in the formula (1)),

2-alkyladamantane-2-yloxycarbonyl group (a group in which R^(a1), R^(a2) and a carbon atom form adamantyl group, and R^(a3) is alkyl group, in the formula (1)), and

1-(adamantane-1-yl)-1-alkylalkoxycarbonyl group (a group in which R^(a1) and R^(a2) are alkyl group, and R^(a3) is adamantyl group, in the formula (1)).

The hydrocarbon group of R^(a1′) to R^(a3′) includes any of an alkyl group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group.

Examples of the aromatic hydrocarbon group include an aryl group such as phenyl, naphthyl, anthryl, p-methylphenyl, p-tert-butylphenyl, p-adamantylphenyl, tolyl, xylyl, cumenyl, mesityl, biphenyl, phenanthryl, 2,6-diethylphenyl and 2-methyl-6-ethylphenyl groups.

Examples of the divalent hydrocarbon group which is formed by bonding with R^(a2′) and R^(a3′) include the same groups as a hydrocarbon group of substituent of ring X¹ in the formula (I) except that one hydrogen atom is remove.

At least one of R^(a1′) and R^(a2′) is preferably a hydrogen atom.

Specific examples of the acid labile group (2) include a group below.

The acid labile monomer (a1) is preferably a monomer having an acid labile group and a carbon-carbon double bond, and more preferably a (meth)acrylic monomer having the acid labile group.

Among the (meth)acrylic monomer having an acid labile group, it is preferably a monomer having a C₅ to C₂₀ alicyclic hydrocarbon group. When a resin which can be obtained by polymerizing monomers having bulky structure such as the alicyclic hydrocarbon group is used, the resist composition having excellent resolution tends to be obtained during the production of a resist pattern.

Examples of the (meth)acrylic monomer having the acid labile group and a carbon-carbon double bond preferably include a monomer represented by the formula (a1-1) and a monomer represented by the formula (a1-2), below (hereinafter may be referred to as a “monomer (a1-1)” and a “monomer (a1-2)”). These may be used as a single monomer or as a combination of two or more monomers. The monomer (a1-1) induces a structural unit represented by the formula (a1-1), and the monomer (a1-2) induces a structural unit represented by the formula (a1-2) as described below (hereinafter may be referred to as the “structural unit (a1-1)” and the “structural unit (a1-2)”).

wherein L^(a1) and L^(a2) independently represent *—O— or *—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, * represents a bond to the carbonyl group;

R^(a4) and R^(a5) independently represent a hydrogen atom or a methyl group;

R^(a6) and R^(a7) independently represent a C₁ to C₈ alkyl group or a C₃ to C₁₀ alicyclic hydrocarbon group;

m1 represents an integer 0 to 14;

n1 represents an integer 0 to 10; and

n1′ represents an integer 0 to 3.

In the formula (a1-1) and the formula (a1-2), L^(a1) and L^(a2) are preferably *—O— or *—O—(CH₂)_(k1′)—CO—O—, here represents an integer of 1 to 4, and more preferably 1, and more preferably *—O—.

R^(a4) and R^(a5) are preferably a methyl group.

Examples of the alkyl group of R^(a6) and R^(a7) include methyl, ethyl, propyl, butyl, pentyl, hexyl and octyl groups. Among these, the alkyl group of R^(a6) and R^(a7) is preferably a C₁ to C₆ alkyl group.

Examples of the alicyclic group of R^(a6) and R^(a7) include the same groups described above. Among these, the alicyclic group of R^(a6) and R^(a7) is preferably a C₃ to C₈ alicyclic hydrocarbon group, and more preferably a C₃ to C₆ alicyclic hydrocarbon group.

m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1′ is preferably 0 or 1, and more preferably 1.

Examples of the monomer (a1-1) include monomers described in JP 2010-204646A. Among these, the monomers are preferably monomers represented by the formula (a1-1-1) to the formula (a1-1-8), and more preferably monomers represented by the formula (a1-1-1) to the formula (a1-1-4) below.

Examples of the monomer (a1-2) include 1-ethylcyclopentane-1-yl (meth)acrylate, 1-ethylcyclohexane-1-yl(meth)acrylate, 1-ethylcycloheptane-1-yl(meth)acrylate, 1-methylcyclopentane-1-yl (meth)acrylate and 1-isopropylcyclopentane-1-yl(meth)acrylate.

Among these, the monomers are preferably monomers represented by the formula (a1-2-1) to the formula (a1-2-6), and more preferably monomers represented by the formula (a1-2-3) and the formula (a1-2-4), and still more preferably monomer represented by the formula (a1-2-3) below.

When the resin (A) contains the structural unit derived from the monomer (a1-1) and/or the structural unit derived from the monomer (a1-2), the total proportion thereof is generally 10 to 95 mol %, preferably 15 to 90 mol %, more preferably 20 to 85 mol %, with respect to the total structural units (100 mol %) of the resin (A).

Examples of a monomer having an acid-labile group (2) and a carbon-carbon double bond include a monomer represented by the formula (a1-5). Such monomer may be hereinafter referred to as “monomer (a1-5)”. When the resin (A2) has the structural unit derived from the monomer (a1-5), a resist pattern tends to be obtained with less defects.

wherein R³¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has a halogen atom;

L¹, L² and L³ independently represent *—O—, *—S— or *—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, * represents a bond to the carbonyl group (—CO—);

s1 represents an integer of 0 to 4;

s1′ represents an integer of 0 to 4;

Z¹ represents a single bond or a C₁ to C₆ alkanediyl group, and one or more —CH₂— contained in the alkanediyl group may be replaced by —O— or —CO—.

In the formula (a1-5), R³¹ is preferably a hydrogen atom, or a methyl group or trifluoromethyl group;

L¹ is preferably —O—;

L² and L³ are independently preferably *—O— or *—S—, and more preferably —O— for one and —S— for another;

s1 is preferably 1;

s1′ is preferably an integer of 0 to 2;

Z¹ is preferably a single bond or —CH₂—CO—O—.

Examples of the compound represented by the formula (a1-5) include compounds below.

When the resin (A) contains the structural unit derived from the monomer represented by the formula (a1-5), the proportion thereof is generally 1 to 50 mol %, preferably 3 to 45 mol %, and more preferably 5 to 40 mol %, with respect to the total structural units (100 mol %) constituting the resin (A).

<Acid Stable Monomer>

As the acid stable monomer, a monomer having a hydroxy group or a lactone ring is preferable. When a resin containing the structural unit derived from a monomer having hydroxy group (hereinafter such acid stable monomer may be referred to as “acid stable monomer (a2)”) or a acid stable monomer having a lactone ring (hereinafter such acid stable monomer may be referred to as “acid stable monomer (a3)”) is used, the adhesiveness of resist to a substrate and resolution of resist tend to be improved.

<Acid Stable Monomer (a2)>

The acid stable monomer (a2), which has the hydroxy group, is preferably selected depending on the kinds of an exposure light source at producing the resist pattern.

When KrF excimer laser lithography (248 nm), or high-energy irradiation such as electron beam or EUV light is used for the resist composition, using the acid stable monomer having a phenolic hydroxy group such as hydroxystyrene as the acid stable monomer (a2) is preferable.

When ArF excimer laser lithography (193 nm), i.e., short wavelength excimer laser lithography is used, using the acid stable monomer having a hydroxy adamantyl group represented by the formula (a2-1) as the acid stable monomer (a2) is preferable.

The acid stable monomer (a2) having the hydroxy group may be used as a single monomer or as a combination of two or more monomers.

Examples of the acid stable monomer having hydroxy adamantyl include the monomer represented by the formula (a2-1).

wherein L^(a3) represents —O— or *—O—(CH₂)_(k2)—CO—O—;

k2 represents an integer of 1 to 7;

* represents a bind to —CO—;

R^(a14) represents a hydrogen atom or a methyl group;

R^(a15) and R^(a16) independently represent a hydrogen atom, a methyl group or a hydroxy group;

o1 represents an integer of 0 to 10.

In the formula (a2-1), Las is preferably —O—, —O—(CH₂)_(f1)—CO—O—, here f1 represents an integer of 1 to 4, and more preferably —O—.

R^(a14) is preferably a methyl group.

R^(a15) is preferably a hydrogen atom.

R^(a16) is preferably a hydrogen atom or a hydroxy group.

o1 is preferably an integer of 0 to 3, and more preferably an integer of 0 or 1.

Examples of the acid stable monomer (a2-1) include monomers described in JP 2010-204646A. Among these, the monomers are preferably monomers represented by the formula (a2-1-1) to the formula (a2-1-6), more preferably monomers represented by the formula (a2-1-1) to the formula (a2-1-4), and still more preferably monomers represented by the formula (a2-1-1) and the formula (a2-1-3) below.

When the resin (A) contains the acid stable structural unit derived from the monomer represented by the formula (a2-1), the proportion thereof is generally 3 to 40 mol %, preferably 5 to 35 mol %, more preferably 5 to 30 mol %, and still more preferably 5 to 20 mol %, with respect to the total structural units (100 mol %) constituting the resin (A).

<Acid Stable Monomer (a3)>

The lactone ring included in the acid stable monomer (a3) may be a monocyclic compound such as β-propiolactone ring, γ-butyrolactone, δ-valerolactone, or a condensed ring with monocyclic lactone ring and other ring. Among these, γ-butyrolactone and condensed ring with γ-butyrolactone and other ring are preferable.

Examples of the acid stable monomer (a3) having the lactone ring include monomers represented by the formula (a3-1), the formula (a3-2) and the formula (a3-3). These monomers may be used as a single monomer or as a combination of two or more monomers.

wherein L^(a4) to L^(a6) independently represent —O— or *—O—(CH₂)_(k3)—CO—O—;

k3 represents an integer of 1 to 7, * represents a bind to —CO—;

R^(a18) to R^(a20) independently represent a hydrogen atom or a methyl group;

R^(a21) in each occurrence represents a C₁ to C₄ alkyl group;

p1 represents an integer of 0 to 5;

R^(a22) to R^(a23) in each occurrence independently represent a carboxyl group, cyano group, and a C₁ to C₄ alkyl group;

q1 and r1 independently represent an integer of 0 to 3.

In the formulae (a3-1) to (a3-3), L^(a4) to L^(a6) include the same group as described in L^(a3) above, and are independently preferably —O—, *—O—(CH₂)_(k3′)—CO—O—, here k3′ represents an integer of 1 to 4 (preferably 1), and more preferably —O—;

R^(a18) to R^(a21) are independently preferably a methyl group.

R^(a22) and R^(a23) are independently preferably a carboxyl group, cyano group or methyl group;

p1 to r1 are independently preferably an integer of 0 to 2, and more preferably an integer of 0 or 1.

Examples of the monomer (a3) include monomers described in JP 2010-204646A. Among these, the monomers are preferably monomers represented by the formula (a3-1-1) to the formula (a3-1-4), the formula (a3-2-1) to the formula (a3-2-4), the formula (a3-3-1) to the formula (a3-3-4), more preferably monomers represented by the formula (a3-1-1) to the formula (a3-1-2), the formula (a3-2-3) to the formula (a3-2-4), and still more preferably monomers represented by the formula (a3-1-1) and the formula (a3-2-3) below.

When the resin (A) contains the structural units derived from the monomer represented by the formula (a3-1), the monomer represented by the formula (a3-2) and/or the monomer represented by the formula (a3-3), the total proportion thereof is preferably 5 to 70 mol %, more preferably 10 to 65 mol %, still more preferably 15 to 60 mol %, with respect to the total structural units (100 mol %) constituting the resin (A).

The resin (A) is preferably a copolymer of the compound (I′), the acid labile monomer (a1) and the acid stable monomer. When the resin (A) is the copolymer of the compound (I′), the acid labile monomer (a1) and the acid stable monomer, the proportion of the structural unit (I) is preferably 10 to 80 mol %, and more preferably 20 to 60 mol % with respect to the total structural units (100 mol %) constituting the resin (A).

The proportion of the structural unit derived from the monomer having an adamantyl group (in particular, the monomer having the acid labile group (a1-1)) is preferably 15 mol % or more with respect to the structural units derived from the compound (I′) and/or the acid labile monomer (a1). As the mole ratio of the structural unit derived from the monomer having an adamantyl group increases within this range, the dry etching resistance of the resulting resist improves.

The resin (A) preferably is a copolymer of the compound (I′), the acid labile monomer (a1) and the acid stable monomer (a2) having a hydroxy group and/or the acid stable monomer (a3) having a lactone ring. In this copolymer, the acid labile monomer (a1) preferably is at least one of the acid labile monomer (a1-1) having an adamantyl group and the acid labile monomer (a1-2) having a cyclohexyl group, and more preferably is the acid labile monomer (a1-1).

The acid stable monomer (a2) is preferably the monomer having the hydroxyadamantyl group (a2-1).

The acid stable monomer (a3) preferably is at least one of the monomer having the γ-butyrolactone ring (a3-1) and the monomer having the condensed ring of the γ-butyrolactone ring and the norbornene ring (a3-2).

The resin (A) can be produced by a known polymerization method, for example, radical polymerization method, using at least one of the compound (I′), and optionally at least one of the acid labile monomer (a1), and/or at least one of the acid stable monomer (a2) having a hydroxy group, and/or at least one of the acid stable monomer (a3) having a lactone ring, and/or at least one of a known compound.

The weight average molecular weight of the resin (A) is preferably 2,500 or more (more preferably 3,000 or more, and still more preferably 4,000 or more), and 50,000 or less (more preferably 30,000 or less, and still more preferably 15,000 or less).

The weight average molecular weight is a value determined by gel permeation chromatography using polystyrene as the standard product. The detailed condition of this analysis is described in Examples.

The resist composition of the present invention may contain at least one resin other than the resin (A), which has at least one of the structural unit derived from the acid labile monomer (a1), the structural unit derived from the acid stable monomer described above and the structural unit derived from a known monomer.

The proportion of the resin (A) can be adjusted with respect to the total solid proportion of the resist composition. For example, the resist composition of the present invention preferably contains 80 weight % or more and 99 weight % or less of the resin (A), with respect to the total solid proportion of the resist composition.

In the specification, the term “solid proportion of the resist composition” means the entire proportion of all ingredients other than the solvent (E). For example, if the proportion of the solvent (E) is 90 weight %, the solid proportion of the resist composition is 10 weight %.

The proportion of the resin (A) and the solid proportion of the resist composition can be measured with a known analytical method such as, for example, liquid chromatography and gas chromatography.

<Acid generator (B)>

An acid generator (B) is classified into non-ionic-based or ionic-based acid generator.

Examples of the non-ionic-based acid generator include organic halogenated compounds; sulfonate esters such as 2-nitrobenzyl ester, aromatic sulfonate, oxime sulfonate, N-sulfonyl oxyimide, sulfonyl oxyketone and diazo naphthoquinone 4-sulfonate; sulfones such as disulfone, ketosulfone and sulfone diazomethane.

Examples of the ionic acid generator includes onium salts containing onium cation (such as diazonium salts, phosphonium salts, sulfonium salts, iodonium salts).

Examples of anion of onium salts include sulfonate anion, sulfonylimide anion and sulfonylmethyde anion.

For the acid generator (B), compounds which generate an acid by radiation described in JP S63-26653-A, JP S55-164824-A, JP S62-69263-A, JP S63-146038-A, JP S63-163452-A, JP S62-153853-A, JP S63-146029-A, U.S. Pat. No. 3,779,778-B, U.S. Pat. No. 3,849,137-B, DE3,914,407-B and EP-126,712-A can be used. Also, the acid generator formed according to conventional methods can be used.

A fluorine-containing acid generator is preferable for the acid generator (B), and a sulfonic acid salt represented by the formula (B1) is more preferable.

wherein Q¹ and Q² independently represent a fluorine atom or a C₁ to C₆ perfluoroalkyl group;

L^(b1) represents a single bond or an C₁ to C₁₇ divalent saturated hydrocarbon group, and one or more —CH₂— contained in the divalent saturated hydrocarbon group may be replaced by —O— or —CO—;

Y represents an optionally substituted C₁ to C₁₈ alkyl group or an optionally substituted C₃ to C₁₈ alicyclic hydrocarbon group, and one or more —CH₂— contained in the alkyl group and alicyclic hydrocarbon group may be replaced by —O—, —CO— or —SO₂—; and

Z+ represents an organic cation.

Examples of the perfluoroalkyl group include trifluoromethyl, perfluoroethyl, perfluoropropyl, perfluoro-isopropyl, perfluorobutyl, perfluoro-sec-butyl, perfluoro-tert-butyl, perfluoropentyl and perfluorohexyl groups.

Among these, Q¹ and Q² independently are preferably trifluoromethyl or fluorine atom, and more preferably a fluorine atom.

Examples of the a divalent saturated hydrocarbon group of L^(b1) include any of;

a chain alkanediyl group such as methylene, ethylene, propane-1,3-diyl, propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl, tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl, heptadecane-1,17-diyl groups, methane-1,1-diyl, ethane-1,1-diyl, propan-1,1-diyl and propan-2,2-diyl groups;

a branched chain alkanediyl group such as a group in which a chain alkanediyl group is bonded a side chain of a C₁ to C₄ alkyl group such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl and tert-butyl, for example, butan-1,3-diyl, 2-methylpropane-1,3-diyl, 2-methylpropane-1,2-diyl, pentane-1,4-diyl, 2-methylbutane-1,4-diyl groups;

a mono-alicyclic saturated hydrocarbon group such as a cycloalkanediyl group (e.g., cyclobutan-1,3-diyl, cyclopentan-1,3-diyl, cyclohexane-1,2-diyl, 1-methylhexane-1,2-diyl, cyclohexane-1,4-diyl, cyclooctan-1,2-diyl, cyclooctan-1,5-diyl groups);

a poly-alicyclic saturated hydrocarbon group such as norbornane-1,4-diyl, norbornane-2,5-diyl, adamantane-1,5-diyl and adamantane-2,6-diyl groups; and

a combination of two or more groups.

Examples of the saturated hydrocarbon group of L^(b1) in which one or more —CH₂— contained in the saturated hydrocarbon group is replaced by —O— or —CO— include groups represented by the formula (b1-1) to the formula (b1-6) below. In the formula (b1-1) to the formula (b1-6), the group is represented so as to correspond with two sides of the formula (B1), that is, the left side of the group bonds to C(Q¹)(Q²)- and the right side of the group bonds to —Y (examples of the formula (b1-1) to the formula (b1-6) are the same as above). * represents a bond.

wherein L^(b2) represents a single bond or a C₁ to C₁₅ divalent saturated hydrocarbon group;

L^(b3) represents a single bond or a C₁ to C₁₂ divalent saturated hydrocarbon group;

L^(b4) represents a C₁ to C₁₃ divalent saturated hydrocarbon group, the total number of the carbon atoms in L^(b3) and L^(b4) is at most 13;

L^(b5) represents a C₁ to C₁₅ divalent saturated hydrocarbon group;

L^(b6) and L^(b7) independently represent a C₁ to C₁₅ divalent saturated hydrocarbon group, the total number of the carbon atoms in L^(b6) and L^(b7) is at most 16;

L^(b8) represents a C₁ to C₁₄ divalent saturated hydrocarbon group;

L^(b9) and L^(b10) independently represent a C₁ to C₁₁ divalent saturated hydrocarbon group, the total number of the carbon atoms in L^(b9) and L^(b10) is at most 12.

Among these, L^(b1) is preferably the groups represented by the formula (b1-1) to the formula (b1-4), more preferably the group represented by the formula (b1-1) or the formula (b1-2), and still more preferably the group represented by the formula (b1-1). In particular, the divalent group represented by the formula (b1-1) in which L^(b2) represents a single bond or —CH₂— is preferable.

Specific examples of the divalent group represented by the formula (b1-1) include groups below. In the formula below, * represent a bond.

Specific examples of the divalent group represented by the formula (b1-2) include groups below.

Specific examples of the divalent group represented by the formula (b1-3) include groups below.

Specific examples of the divalent group represented by the formula (b1-4) include a group below.

Specific examples of the divalent group represented by the formula (b1-5) include groups below.

Specific examples of the divalent group represented by the formula (b1-6) include groups below.

Examples of the alkyl group of Y include methyl, ethyl, 1-methylethyl, 1,1-dimethylethyl, 2,2-dimethylethyl, propyl, 1-methylpropyl, 2,2-dimethylpropyl, 1-ethylpropyl, butyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-propylbutyl, pentyl, 1-methylpentyl, hexyl, 1,4-dimethylhexyl, heptyl, 1-methylheptyl, octyl, methyloctyl, methylnonyl, 2-ethylhexyl, nonyl, decyl, undecyl and dodecyl groups.

The alkyl group of Y is preferably a C₁ to C₆ alkyl group.

Examples of the alicyclic hydrocarbon group of Y include groups represented by the formula (Y1) to the formula (Y11).

Y may have a substituent.

Examples of the substituent of Y include a halogen atom, a hydroxy group, an oxo group, a C₁ to C₁₂ alkyl group, a hydroxy group-containing C₁ to C₁₂ alkyl group, a C₃ to C₁₆ alicyclic hydrocarbon group, a C₁ to C₁₂ alkoxy group, a C₆ to C₁₈ aromatic hydrocarbon group, a C₇ to C₂₁ aralkyl group, a C₂ to C₄ acyl group, a glycidyloxy group or a —(CH₂)_(j2)—O—CO—R^(b1) group, wherein R^(b1) represents a C₁ to C₁₆ alkyl group, a C₃ to C₁₆ alicyclic hydrocarbon group or a C₆ to C₁₈ aromatic hydrocarbon group, j2 represents an integer of 0 to 4. The alkyl group, alicyclic hydrocarbon group, aromatic hydrocarbon group and the aralkyl group of the substituent may further have a substituent such as a C₁ to C₆ alkyl group, a halogen atom, a hydroxy group and an oxo group.

Examples of the hydroxy group-containing alkyl group include hydroxymethyl and hydroxyethyl groups

Examples of the aralkyl group include benzyl, phenethyl, phenylpropyl, naphthylmethyl and naphthylethyl groups.

Examples of alicyclic hydrocarbon group of Y in which one or more —CH₂— contained in the alicyclic hydrocarbon group is replaced by —O—, —CO— or —SO₂— include groups represented by the formula (Y12) to the formula (Y26).

Among these, the alicyclic hydrocarbon group is preferably any one of groups represented by the formula (Y1) to the formula (Y19), more preferably any one of groups represented by the formula (Y11), (Y14), (Y15) or (Y19), and still more preferably group represented by the formula (Y11) or (Y14).

Examples of Y include the groups below.

When Y represents an alkyl group and L^(b1) represents a C₁ to C₁₇ divalent alicyclic hydrocarbon group, the —CH₂— contained in the divalent alicyclic hydrocarbon group bonding Y is preferably replaced by an oxygen atom or carbonyl group. In this case, the —CH₂— contained in the alkyl group constituting Y is not replaced by an oxygen atom or carbonyl group.

Y is preferably an optionally substituted C₃ to C₁₈ alicyclic hydrocarbon group, more preferably an adamantyl group which is optionally substituted, for example, an oxo group, and still more preferably an adamantyl group, a hydroxyadamantyl group and an oxoadamantyl group.

The sulfonate anion is preferably an anions represented by the formula (b1-1-1) to the formula (b1-1-9) below. In the formula (b1-1-1) to the formula (b1-1-9), Q¹, Q² and L^(b2) represents the same meaning as defined above. R^(b2) and R^(b3) independently represent a C₁ to C₄ alkyl group (preferably methyl group).

Specific examples of the sulfonate anion include sulfonate anions described in JP2010-204646A.

Examples of the cation of the acid generator (B) include an organic onium cation, for example, organic sulfonium cation, organic iodonium cation, organic ammonium cation, benzothiazolium cation and organic phosphonium cation. Among these, organic sulfonium cation and organic iodonium cation are preferable, and aryl sulfonium cation is more preferable.

Z+ of the formula (B1) is preferably represented by any of the formula (b2-1) to the formula (b2-4).

wherein R^(b4), R^(b5) and R^(b6) independently represent a C₁ to C₃₀ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group or a C₆ to C₁₈ aromatic hydrocarbon group, the alkyl group may be substituted with a hydroxy group, a C₁ to C₁₂ alkoxy group or a C₆ to C₁₈ aromatic hydrocarbon group, the alicyclic hydrocarbon group may be substituted with a halogen atom, a C₂ to C₄ acyl group and a glycidyloxy group, the aromatic hydrocarbon group may be substituted with a halogen atom, a hydroxy group, a C₁ to C₁₅ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group or a C₁ to C₁₂ alkoxy group;

R^(b7) and R^(b8) in each occurrence independently represent a hydroxy group, a C₁ to C₁₂ alkyl group or a C₁ to C₁₂ alkoxyl group;

m2 and n2 independently represent an integer of 0 to 5;

R^(b9) and R^(b10) independently represent a C₁ to C₁₈ alkyl group or a C₃ to C₁₈ alicyclic hydrocarbon group, or R^(b9) and R^(b10) may be bonded together with a sulfur atom bonded thereto to form a sulfur-containing 3- to 12-membered (preferably 3- to 7-membered) ring, and one or more —CH₂— contained in the ring may be replaced by —O—, —S— or —CO—;

R^(b11) represents a hydrogen atom, a C₁ to C₁₈ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group or a C₆ to C₁₈ aromatic hydrocarbon group;

R^(b12) represents a C₁ to C₁₂ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group and a C₆ to C₁₈ aromatic hydrocarbon group, the aromatic hydrocarbon group may be substituted with a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxy group, a C₃ to C₁₈ alicyclic hydrocarbon group or a C₁ to C₁₂ alkyl carbonyloxy group;

R^(b11) and R^(b12) may be bonded together with —CH—CO— bonded thereto to form a 3- to 12-membered (preferably a 3- to 7-membered) ring, and one or more —CH₂— contained in the ring may be replaced by —O—, —S— or —CO—;

R^(b13), R^(b14), R^(b15), R^(b16), R^(b17) and R^(b18) in each occurrence independently represent a hydroxy group, a C₁ to C₁₂ alkyl group or a C₁ to C₁₂ alkoxy group;

L^(b11) represents —S— or —O—;

o2, p2, s2 and t2 independently represent an integer of 0 to 5;

q2 or r2 independently represent an integer of 0 to 4;

u2 represents an integer of 0 or 1.

Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl and 2-ethylhexyl groups. In particular, the alkyl group of R^(b9) to R^(b11) is preferably a C₁ to C₁₂ alkyl group.

Examples of the alicyclic hydrocarbon group include a monocyclic hydrocarbon groups such as cyclopropyl, cyclobutyl, cycloheptyl, cyclohexyl, cycloheptyl, cyclodecyl, 2-alkyl-2-adamantyl, 1-(1-adamatyl)-1-alkyl and isobornyl groups. In particular, the alicyclic hydrocarbon group of R^(b9) to R^(b11) is preferably a C₃ to C₁₈ alicyclic hydrocarbon group and more preferably a C₄ to C₁₂ alicyclic hydrocarbon group.

Examples of the aromatic hydrocarbon group include phenyl, naphthyl, 4-methylphenyl, 4-ethylphenyl, 4-t-butylphenyl, 4-cyclohexylphenyl, 4-methoxyphenyl and biphenyl groups.

Examples of the aromatic group substituted with an alkyl group typically represent an aralkyl group such as benzyl and phenethyl groups.

Examples of the alkyl carbonyloxy group of the R^(b12) include methyl carbonyloxy, ethyl carbonyloxy, n-propyl carbonyloxy, isopropyl carbonyloxy, n-butyl carbonyloxy, sec-butyl carbonyloxy, tert-butyl carbonyloxy, pentyl carbonyloxy, hexyl carbonyloxy, octylcarbonyloxy and 2-ethylhexylcarbonyloxy groups.

Examples of the ring having —CH—CO— and formed by R^(b9) and R^(b10) bonded together include thiolane-1-ium ring (tetrahydrothiophenium ring), thian-1-ium ring and 1,4-oxathian-4-ium ring.

Examples of the ring having a sulfur atom and formed by R^(b11) and R^(b12) bonded together include oxocycloheptane ring, oxocyclohexane ring, oxonorbornane ring and oxoadamantane ring.

Among the cations represented by the formula (b2-1) to the formula (b2-4), the cation represented by the formula (b2-1-1) is preferable, and triphenyl sulfonium cation (v2=w2=×2=0 in the formula (b2-1-1)), diphenyltolyl sulfonium cation (v2=w2=0, x2=1, and R^(b21) is a methyl group in the formula (b2-1-1)) and tritolyl sulfonium cation (v2=w2=×2=1, R^(b19), R^(b20) and R^(b21) are a methyl group in the formula (b2-1-1)) are more preferable.

wherein R^(b19), R^(b20) and R^(b21) in each occurrence independently represent a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₃ to C₁₈ alicyclic hydrocarbon group or a C₁ to C₁₂ alkoxy group, and the alkyl group, the alicyclic hydrocarbon group and the alkoxy group may be substituted with a halogen group, a hydroxy group, a C₁ to C₁₂ alkoxy group, a C₆ to C₁₈ aromatic hydrocarbon group, a C₂ to C₄ acyl group or a glycidyloxy group;

v2 to x2 independently represent an integer of 0 to 5.

In the formula (b2-1-1), R^(b19) to R^(b21) independently preferably represent a halogen atom (and more preferably fluorine atom), a hydroxy group, a C₁ to C₁₂ alkyl group or a C₁ to C₁₂ alkoxy group; and

v2 to x2 independently represent preferably 0 or 1.

Specific examples of the organic cations represented by the formula (b2-1) to the formula (b2-4) include, for example, compounds described in JP2010-204646A.

The acid generator (B1) is a compound combined the above sulfonate anion with an organic cation.

The above sulfonate anion and the organic cation may optionally be combined, a combination of any of the anion represented by the formula (b1-1-1) to the formula (b1-1-9) and the cation represented by the formula (b2-1-1), as well as a combination of any of the anion represented by the formula (b1-1-3) to the formula (b1-1-5) and the cation represented by the formula (b2-3) are preferable.

Preferred acid generators (B1) are represented by the formula (B1-1) to the formula (B1-17). Among these, the formulae (B1-1), (B1-2), (B1-6), (B1-11), (B1-12), (B1-13) and (B1-14) which contain triphenyl sulfonium cation, and the formulae (B1-3) and (B1-7) which contain tritolyl sulfonium cation are preferable.

In the resist composition of the present invention, the proportion of the acid generator (B) is preferably not less than 1 parts by weight (and more preferably not less than 3 parts by weight), and not more than 30 parts by weight (and more preferably not more than 25 parts by weight), with respect to 100 parts by weight of the resin (A).

<Compound (II)>

The compound (II) is the compound represented by the formula (II) below.

wherein R³ and R⁴ in each occurrence independently represent a C₁ to C₁₂ hydrocarbon group, a C₁ to C₆ alkoxyl group, a C₂ to C₇ acyl group, a C₂ to C₇ acyloxy group, a C₂ to C₇ alkoxycarbonyl group, a nitro group or a halogen atom; m and n independently represent an integer of 0 to 4.

Examples of the alkoxycarbonyl group include methoxycarbonyl, ethoxycarbonyl, n-propoxycarbonyl, isopropoxycarbonyl, n-butoxycarbonyl, sec-butoxycarbonyl, and tert-butoxycarbonyl groups.

In the formula (II), R³ and R⁴ in each occurrence independently preferably represent a C₁ to C₆ hydrocarbon group, a C₁ to C₄ alkoxyl group, a C₂ to C₅ acyl group, a C₂ to C₅ acyloxy group, a C₂ to C₅ alkoxycarbonyl group, a nitro group or a halogen atom.

m and n independently preferably represent an integer of 0 to 3, and more preferably an integer of 0 to 2.

Specific examples of the compound (II) include compounds below.

In the resist composition of the present invention, the proportion of the compound (II) is preferably 0.01 to 5 weight %, and more preferably 0.01 to 3 weight %, and still more preferably 0.01 to 1 weight % with respect to total solid proportion of the resist composition.

<Solvent (E)>

The resist composition of the present invention may include a solvent (E) in the amount of 90 weight % or more, preferably 92 weight % or more, and more preferably 94 weight % or more, and 99.9 weight % or less, preferably 99 weight % or less in the composition.

The content of the solvent (E) can be measured with a known analytical method such as, for example, liquid chromatography and gas chromatography.

Examples of the solvent (E) include glycol ether esters such as ethylcellosolve acetate, methylcellosolve acetate and propylene glycol monomethyl ether acetate; glycol ethers such as propylene glycol monomethyl ether; esters such as ethyl lactate, butyl acetate, amyl acetate and ethyl pyruvate; ketones such as acetone, methyl isobutyl ketone, 2-heptanone and cyclohexanone; and cyclic esters such as γ-butyrolactone. These solvents (E) can be used as a single solvent or as a combination of two or more solvents.

<Basic Compound (C)>

The resist composition of the present invention may contain a basic compound (C). The basic compound (C) is a compound having a property to quench an acid, in particular, generated from the acid generator (B), and called “quencher”.

As the basic compounds (C), nitrogen-containing basic compounds (for example, amine and basic ammonium salt) are preferable. The amine may be an aliphatic amine or an aromatic amine. The aliphatic amine includes any of a primary amine, secondary amine and tertiary amine. The aromatic amine includes an amine in which an amino group is bonded to an aromatic ring such as aniline, and a hetero-aromatic amine such as pyridine.

Preferred basic compounds (C) include compounds presented by the formula (C₁) to the formula (C₈) as described below. Among these, the basic compound presented by the formula (C₁-1) is more preferable.

wherein R^(c1), R^(c2) and R^(c3) independently represent a hydrogen atom, a C₁ to C₆ alkyl group, C₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀ aromatic hydrocarbon group, one or more hydrogen atom contained in the alkyl group and alicyclic hydrocarbon group may be replaced by a hydroxy group, an amino group or a C₁ to C₆ alkoxyl group, one or more hydrogen atom contained in the aromatic hydrocarbon group may be replaced by a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxyl group, a C₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀ aromatic hydrocarbon group.

wherein R^(c2) and R^(c3) have the same definition of the above;

R^(c4) in each occurrence represents a C₁ to C₆ alkyl group, a C₁ to C₆ alkoxyl group, a C₅ to C₁₀ alicyclic hydrocarbon group or a C₆ to C₁₀ aromatic hydrocarbon group;

m3 represents an integer 0 to 3.

wherein R^(c5), R^(c6), R^(c7) and R^(c8) independently represent the any of the group as described in R^(d1) of the above;

R^(c9) in each occurrence independently represents a C₁ to C₆ alkyl group, a C₃ to C₆ alicyclic hydrocarbon group or a C₂ to C₆ alkanoyl group;

n3 represents an integer of 0 to 8.

Examples of the alkanoyl group include acetyl group, 2-methylacetyl group, 2,2-dimethylacetyl group, propionyl group, butylyl group, isobutylyl group, pentanoyl group, and 2,2-dimethylpropionyl group.

wherein R^(c10), R^(c11), R^(c12), R^(c13) and R^(c16) independently represent the any of the groups as described in R^(c1);

R^(c14), R^(c15) and R^(c17) in each occurrence independently represent the any of the groups as described in R^(c4);

o3 and p3 represent an integer of 0 to 3;

L^(c1) represents a divalent C₁ to C₆ alkanediyl group, —CO—, —C(═NH)—, —S— or a combination thereof.

wherein R^(c18), R^(c19) and R^(c20) in each occurrence independently represent the any of the groups as described in R^(c4);

q3, r3 and s3 represent an integer of 0 to 3;

L^(c2) represents a single bond, a C₁ to C₆ alkanediyl group, —CO—, —C(═NH)—, —S— or a combination thereof.

Specific examples of the amine represented by the formula (C₁) include 1-naphtylamine and 2-naphtylamine, aniline, diisopropylaniline, 2-, 3- or 4-methylaniline, 4-nitroaniline, N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, triethylamine, trimethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, methyldibutylamine, methyldipentylamine, methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine, methyldinonylamine, methyldidecylamine, ethyldibutylamine, ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine, ethyldioctylamine, ethyldinonylamine, ethyldidecylamine, dicyclohexylmethylamine, tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine, ethylene diamine, tetramethylene diamine, hexamethylene diamine, 4,4′-diamino-1,2-diphenylethane, 4,4′-diamino-3,3′-dimethyldiphenylmethane and 4,4′-diamino-3,3′-diethyldiphenylmethane.

Among these, diisopropylaniline is preferable, particularly 2,6-diisopropylaniline is more preferable as the basic compounds (C) contained in the present resist composition.

Specific examples of the compound represented by the formula (C₂) include, for example, piperadine.

Specific examples of the compound represented by the formula (C₃) include, for example, morpholine.

Specific examples of the compound represented by the formula (C₄) include, for example, piperidine, a hindered amine compound having piperidine skeleton described in JP H11-52575-A.

Specific examples of the compound represented by the formula (C₅) include, for example, 2,2′-methylenebisaniline.

Specific examples of the compound represented by the formula (C₆) include, for example, imidazole and 4-methylimidazole.

Specific examples of the compound represented by the formula (C₇) include, for example, pyridine and 4-methylpyrizine.

Specific examples of the compound represented by the formula (C₈) include, for example, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane, 1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane, di(2-pyridyl)ketone, 4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide, 2,2′-dipyridylamine, 2,2′-dipicolylamine and bi pyridine.

Examples of the ammonium salt include tetramethylammonium hydroxide, tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, phenyltrimethyl ammonium hydroxide, 3-(trifluoromethyl)phenyltrimethylammonium hydroxide, tetra-n-butyl ammonium salicylate and choline.

The proportion of the basic compound (C) is preferably 0.01 to 5 weight %, more preferably 0.01 to 3 weight %, and still more preferably 0.01 to 1 weight % with respect to the total solid proportion of the resist composition.

<Other Ingredient (Hereinafter May be Referred to as “Other Ingredient (F)”>

The resist composition can also include small amounts of various additives such as sensitizers, dissolution inhibitors, surfactants, stabilizers, and dyes, as needed.

<Preparing the Resist Composition>

The present resist composition can be prepared by mixing the resin (A), the acid generator (B) and the compound (II), and the basic compound (C), the solvent (E) and the other ingredient (F) as needed. There is no particular limitation on the order of mixing. The mixing may be performed in an arbitrary order. The temperature of mixing may be adjusted to an appropriate temperature within the range of 10 to 40° C., depending on the kinds of the resin and solubility in the solvent (E) of the resin. The time of mixing may be adjusted to an appropriate time within the range of 0.5 to 24 hours, depending on the mixing temperature. There is no particular limitation to the tool for mixing. An agitation mixing may be adopted.

After mixing the above ingredients, the present resist compositions can be prepared by filtering the mixture through a filter having about 0.003 to 0.2 μm pore diameter.

<Method for Producing Resist Pattern>

The method for producing resist pattern of the present invention includes the steps of:

(1) applying the resist composition of the present invention onto a substrate;

(2) drying the applied composition to form a composition layer;

(3) exposing the composition layer;

(4) heating the exposed composition layer, and

(5) developing the heated composition layer.

Applying the resist composition onto the substrate can generally be carried out through the use of a resist application device, such as a spin coater known in the field of semiconductor microfabrication technique. The thickness of the applied resist composition layer can be adjusted by controlling the variable conditions of the resist application device. These conditions can be selected based on a pre-experiment carried out beforehand. The substrate can be selected from various substrates intended to be microfabricated. The substrate may be washed, and an organic antireflection film may be formed on the substrate by use of a commercially available antireflection composition, before the application of the resist composition.

Drying the applied composition layer, for example, can be carried out using a heating device such as a hotplate (so-called “prebake”), a decompression device, or a combination thereof. Thus, the solvent evaporates from the resist composition and a composition layer with the solvent removed is formed. The condition of the heating device or the decompression device can be adjusted depending on the kinds of the solvent used. The temperature in this case is generally within the range of 50 to 200° C. Moreover, the pressure is generally within the range of 1 to 1.0×10⁵ Pa.

The composition layer thus obtained is generally exposed using an exposure apparatus or a liquid immersion exposure apparatus. The exposure is generally carried out through a mask that corresponds to the desired pattern. Various types of exposure light source can be used, such as irradiation with ultraviolet lasers such as KrF excimer laser (wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm), F₂ excimer laser (wavelength: 157 nm), or irradiation with far-ultraviolet wavelength-converted laser light from a solid-state laser source (YAG or semiconductor laser or the like), or vacuum ultraviolet harmonic laser light or the like. Also, the exposure device may be one which irradiates electron beam or extreme-ultraviolet light (EUV).

After exposure, the composition layer is subjected to a heat treatment (so-called “post-exposure bake”) to promote the deprotection reaction. The heat treatment can be carried out using a heating device such as a hotplate. The heating temperature is generally in the range of 50 to 200° C., preferably in the range of 70 to 150° C.

The composition layer is developed after the heat treatment, generally with an alkaline developing solution and using a developing apparatus. The development here means to bring the composition layer after the heat treatment into contact with an alkaline solution. Thus, the exposed portion of the composition layer is dissolved by the alkaline solution and removed, and the unexposed portion of the composition layer remains on the substrate, whereby producing a resist pattern. Here, as the alkaline developing solution, various types of aqueous alkaline solutions used in this field can be used. Examples include aqueous solutions of tetramethylammonium hydroxide and (2-hydroxyethyl)trimethylammonium hydroxide (common name: choline).

After the development, it is preferable to rinse the substrate and the pattern with ultrapure water and to remove any residual water thereon.

<Application>

The resist composition of the present invention is useful as the resist composition for excimer laser lithography such as with ArF, KrF or the like, and the resist composition for electron beam (EB) exposure lithography and extreme-ultraviolet (EUV) exposure lithography, as well as liquid immersion exposure lithography.

The resist composition of the present invention can be used in semiconductor microfabrication and in manufacture of liquid crystals, thermal print heads for circuit boards and the like, and furthermore in other photofabrication processes, which can be suitably used in a wide range of applications.

EXAMPLES

The present invention will be described more specifically by way of examples, which are not construed to limit the scope of the present invention.

All percentages and parts expressing the content or amounts used in the Examples and Comparative Examples are based on weight, unless otherwise specified.

The composition ratio of the resin (the copolymerization ratio of the structural unit derived from each monomer used in the preparation with respect to the resin) was calculated by measuring the amount of the unreacted monomer in the reacted solution after the completion of the reaction through liquid chromatography, and calculating the amount of the monomer use in the polymerization from the obtained results.

The weight average molecular weight is a value determined by gel permeation chromatography.

Columun: TSK gel Multipore HXL-M×3+guardcolumn (Tosoh Co. Ltd.)

Eluant: tetrahydrofuran

Flow rate: 1.0 mL/min

Detecting device: RI detector

Column temperature: 40° C.

Injection amount: 100 μL

Standard material for calculating molecular weight: standard polysthylene (Toso Co. ltd.)

Synthetic Example of the Resin

The monomers used the synthesis of the resin are shown below.

Synthesis of Resin A1

Monomer (D), monomer (E), monomer (B), monomer (K), monomer (C) and monomer (F) were mixed together with a mole ratio of monomer (D): monomer (E): monomer (B): monomer (K): monomer (C): monomer (F)=28:14:6:5:31:16, and dioxane was added thereto in an amount equal to 1.5 times by weight of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain a solution in an amount of 1 mol % and 3 mol % respectively with respect to the entire amount of monomers, and the resultant mixture was heated for about 5 hours at 73° C. After that, the obtained reacted mixture was poured into a mixture of a large amount of methanol and water (weight ratio of methanol: water=4:1) to precipitate a resin. The obtained resin was filtrated. Thus obtained resin was dissolved in another dioxane to obtain a solution, and the solution was poured into a mixture of methanol and water to precipitate a resin. The obtained resin was filtrated. These operations were repeated 2 times, resulting in a 81% yield of copolymer having a weight average molecular weight of about 7600. This copolymer, which had the structural units of the following formula, was referred to Resin A1.

Synthesis of Resin A2

Monomer (D), monomer (E), monomer (B), monomer (K) and monomer (C) were mixed together with a mole ratio of monomer (D): monomer (E): monomer (B): monomer (K): monomer (C)=28:14:10:10:38, and dioxane was added thereto in an amount equal to 1.5 times by weight of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain a solution in an amount of 1 mol % and 3 mol % respectively with respect to the entire amount of monomers, and the resultant mixture was heated for about 5 hours at 75° C. After that, the obtained reacted mixture was poured into a mixture of a large amount of methanol and water (weight ratio of methanol: water=4:1) to precipitate a resin. The obtained resin was filtrated. Thus obtained resin was dissolved in another dioxane to obtain a solution, and the solution was poured into a mixture of methanol and water to precipitate a resin. The obtained resin was filtrated. These operations were repeated 2 times, resulting in a 76% yield of copolymer having a weight average molecular weight of about 7200. This copolymer, which had the structural units of the following formula, was referred to Resin A2.

Synthesis of Resin A3

Monomer (A), monomer (E), monomer (B), monomer (K) and monomer (C) were mixed together with a mole ratio of monomer (A): monomer (E): monomer (B): monomer (K): monomer (C)=25:18:3:9:45, and dioxane was added thereto in an amount equal to 1.5 times by weight of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain a solution in an amount of 1 mol % and 3 mol % respectively with respect to the entire amount of monomers, and the resultant mixture was heated for about 5 hours at 75° C. After that, the obtained reacted mixture was poured into a mixture of a large amount of methanol and water (weight ratio of methanol: water=4:1) to precipitate a resin. The obtained resin was filtrated. Thus obtained resin was dissolved in another dioxane to obtain a solution, and the solution was poured into a mixture of methanol and water to precipitate a resin. The obtained resin was filtrated. These operations were repeated 2 times, resulting in a 70% yield of copolymer having a weight average molecular weight of about 7600. This copolymer, which had the structural units of the following formula, was referred to Resin A3.

Synthesis of Resin A4

Monomer (A), monomer (B) and monomer (C) were mixed together with a mole ratio of monomer (A): monomer (B): monomer (C)=50:25:25, and dioxane was added thereto in an amount equal to 1.5 times by weight of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain a solution in an amount of 1 mol % and 3 mol % respectively with respect to the entire amount of monomers, and the resultant mixture was heated for about 8 hours at 80° C. After that, the obtained reacted mixture was poured into a mixture of a large amount of methanol and water (weight ratio of methanol: water=4:1) to precipitate a resin. The obtained resin was filtrated. Thus obtained resin was dissolved in another dioxane to obtain a solution, and the solution was poured into a mixture of methanol and water to precipitate a resin. The obtained resin was filtrated. These operations were repeated 3 times, resulting in a 60% yield of copolymer having a weight average molecular weight of about 9200. This copolymer, which had the structural units of the following formula, was referred to Resin A4.

Synthesis of Resin A5

Monomer (A), monomer (G), monomer (B), monomer (K) and monomer (C) were mixed together with a mole ratio of monomer (A): monomer (G): monomer (B): monomer (K): monomer (C)=25:18:3:9:45, and dioxane was added thereto in an amount equal to 1.5 times by weight of the total amount of monomers to obtain a solution. Azobisisobutyronitrile and azobis(2,4-dimethylvaleronitrile) was added as an initiator to obtain a solution in an amount of 1 mol % and 3 mol % respectively with respect to the entire amount of monomers, and the resultant mixture was heated for about 5 hours at 75° C. After that, the obtained reacted mixture was poured into a mixture of a large amount of methanol and water (weight ratio of methanol: water=4:1) to precipitate a resin. The obtained resin was filtrated. Thus obtained resin was dissolved in another dioxane to obtain a solution, and the solution was poured into a mixture of methanol and water to precipitate a resin. The obtained resin was filtrated. These operations were repeated 2 times, resulting in a 78% yield of copolymer having a weight average molecular weight of about 7500. This copolymer, which had the structural units of the following formula, was referred to Resin A5.

(Preparing Resist Composition)

Resist compositions were prepared by mixing and dissolving each of the components shown in Table 1, and then filtrating through a fluororesin filter having 0.2 μm pore diameter.

TABLE 1 (Unit: parts) Resin Acid Generator Compound BP/PEB(° C./° C.) Ex. 1 A1 = 10 B1 = 1.0 E1 = 0.1 95/85 Ex. 2 A2 = 10 B1 = 1.0 E1 = 0.1 95/85 Ex. 3 A3 = 10 B1 = 1.0 E1 = 0.1 110/105 Ex. 4 A3 = 10 B2 = 1.0 E1 = 0.1 110/105 Ex. 5 A5 = 10 B1 = 1.0 E1 = 0.1 110/105 Comp. A4 = 10 B2 = 1.0 C1 = 0.1 110/105 Ex. 1

<Resin>

A1 to A5: Resin A1 to Resin A5 prepared by the Synthetic Examples

<Acid Generator>

Acid generator B1: this was prepared by a method according to the method described in the Examples of JP2010-152341A

Acid generator B2: this was prepared by a method according to the method described in the Examples of JP2007-161707A

<Basic Compound: Qencher>

C1: 2,6-diisopropylaniline (obtained from Tokyo Chemical Industry Co., LTD)

<Compound (II)>

E1: obtained from Tokyo Chemical Industry Co., LTD

<Solvent of Resist Composition>

Propylene glycol monomethyl ether acetate 265 parts  Propylene glycol monomethyl ether 20 parts 2-Heptanone 20 parts γ-butyrolactone 3.5 parts 

(Producing Resist Pattern)

A composition for an organic antireflective film (“ARC-29”, by Nissan Chemical Co. Ltd.) was applied onto 12-inch silicon wafers and baked for 60 seconds at 205° C. to form a 78 nm thick organic antireflective film.

The above resist compositions were then applied thereon by spin coating so that the thickness of the resulting film became 85 nm after drying.

The obtained wafers were then pre-baked for 60 sec on a direct hot plate at the temperatures given in the “PB” column in Table 1 to form a composition layer.

Line and space patterns were then exposed through stepwise changes in exposure quantity using an ArF excimer stepper for immersion lithography (“XT:1900Gi” by ASML Ltd.: NA=1.35, ¾ Annular, X-Y deflection), on the wafers on which the composition layer had thus been formed.

The exposure was followed by 60 seconds of post-exposure baking at the temperatures given in the “PEB” column in Table 1.

This was followed by 60 sec of puddle development with 2.38 wt % tetramethylammonium hydroxide aqueous solution to form a resist pattern.

Effective sensitivity was represented as the exposure amount at which a 50 nm line and space pattern resolved to 1:1 with the each resist film.

(Focus Margin (DOF) Evaluation)

For the effective sensitivity, when the focus was gradated to form a resist pattern with a standard width as the range with a line width of 50 nm±5% (47.5 to 52.5 nm),

a “◯◯” was given when the DOF value was z 0.17 μm,

a “◯” was given when the DOF value was z 0.10 μm, and

an “x” was given when the DOF value was <0.10 μm.

Table 2 gives the there results. The parenthetical number means DOF values.

(Line Edge Roughness (LER) Evaluation)

When the wall surface of the resist pattern following the lithography process was observed using a scanning electron microscope,

a “◯◯” was given if the irregularity in the resist pattern side wall have a roughness width ≦4 nm,

a “◯” was given when the roughness width was >4 nm and ≦4.5 nm, and

an “x” was given when the roughness width was >4.5 nm.

Table 2 gives the there results. The parenthetical number means roughness width values.

TABLE 2 DOF LER Ex. 1 ∘∘(0.24) ∘∘(3.24) Ex. 2 ∘∘(0.21) ∘∘ (3.33) Ex. 3 ∘∘(0.21) ∘∘ (3.21) Ex. 4 ∘(0.12) ∘(4.02) Ex. 5 ∘∘(0.24) ∘∘(3.18) Comp. Ex. 1 x(0.03) x(6.38)

According to the resin and the resist composition of the present invention, it is possible to achieve satisfactory wide focus margin (DOF) and excellent pattern line edge roughness in the obtained resist pattern. Therefore, the present resist composition can be used for semiconductor microfabrication. 

1. A resist composition comprising (A) a resin having a structural unit represented by the formula (I), (B) an acid generator and (D) a compound represented by the formula (II).

wherein R¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms; ring X¹ represents a C₂ to C₃₆ heterocyclic group, one or more hydrogen atoms contained in the heterocyclic group may be replaced by a halogen atom, a hydroxy group, a C₁ to C₂₄ hydrocarbon, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group;

wherein R³ and R⁴ in each occurrence independently represent a C₁ to C₁₂ hydrocarbon group, a C₁ to C₆ alkoxyl group, a C₂ to C₇ acyl group, a C₂ to C₇ acyloxy group, a C₂ to C₇ alkoxycarbonyl group, a nitro group or a halogen atom; m and n independently represent an integer of 0 to
 4. 2. The resist composition according to claim 1, wherein the structural unit represented by the formula (I) is a structural unit represented by the formula (IA);

wherein R²³ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms; R²⁴ and R²⁵ in each occurrence independently represent a hydrogen atom or a C₁ to C₂₄ hydrocarbon group, and R²⁶ to R²⁹ independently represent a hydrogen atom or a C₁ to C₂₄ hydrocarbon group, or at least two of R²⁴ to R²⁹ may be bonded together to form a C₃ to C₃₀ ring, one or more hydrogen atoms contained in the hydrocarbon group or the ring may be replaced by a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group, and one or more —CH₂— contained in the hydrocarbon group or the ring may be replaced by —CO— or —O—; n′ represents an integer of 0 to
 3. 3. The resist composition according to claim 1, wherein the structural unit represented by the formula (I) is a structural unit represented by the formula (IB);

wherein R³⁹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms; R⁴⁰, R⁴¹, R⁴⁷ and R⁴⁸ in each occurrence independently represent a hydrogen atom or a C₁ to C₂₄ hydrocarbon group, and R⁴² to R⁴⁶ and R⁴⁹ independently represent a hydrogen atom or a C₁ to C₁₂ hydrocarbon group, or at least two of R⁴⁰ to R⁴⁹ may be bonded together to form a C₃ to C₂₄ ring, one or more hydrogen atoms contained in the hydrocarbon group or the ring may be replaced by a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group, and one or more —CH₂— contained in the hydrocarbon group or the ring may be replaced by —CO— or —O—; n4 and n5 independently represent an integer of 0 to
 3. 4. The resist composition according to claim 1, wherein the structural unit represented by the formula (I) is a structural unit represented by the formula (ID);

wherein R³¹ represents a hydrogen atom, a halogen atom or a C₁ to C₆ alkyl group that optionally has one or more halogen atoms; R³² in each occurrence independently represents a halogen atom, a hydroxy group, a C₁ to C₁₂ alkyl group, a C₁ to C₁₂ alkoxyl group, a C₂ to C₄ acyl group or a C₂ to C₄ acyloxy group; n9 represents an integer of 0 to
 8. 5. The resist composition according to claim 1, which further comprises a solvent.
 6. A method for producing resist pattern comprising steps of; (1) applying the resist composition of claim 1 onto a substrate; (2) drying the applied composition to form a composition layer; (3) exposing the composition layer; (4) heating the exposed composition layer, and (5) developing the heated composition layer. 